Heretofore, there is known a hermetically sealed battery (a “sealed battery”) including a battery case formed with a through hole such as a liquid inlet used for injection of an electrolyte, an electrode body accommodated in this battery case, and a sealing member that hermetically seals the through hole of the battery case from the outside. One example of the sealing member is formed of a metallic lid member. This sealing member (a metallic lid member) 915 is welded, at its circumferential edge portion 915m, over the whole circumference to an annular surrounding portion 913m surrounding a liquid inlet (a through hole) 913e of a battery case 913 as shown in FIG. 23, thereby hermetically sealing the liquid inlet 913e from outside (from above in FIG. 23).
Regarding this sealing member 915, however, when the circumferential edge portion 915m of the sealing member 915 is welded to the surrounding portion 913m of the battery case 913, the electrolyte stuck to the surrounding portion 913m and the electrolyte evaporated by heat during welding may cause sealing failures (welding failures). Thus, it is difficult to reliably hermetically seal the liquid inlet 913e by welding of the whole circumference of the sealing member 915.
Another sealed battery uses, as shown in FIG. 24, a sealing member 925 including the aforementioned metallic lid member 915 joined with a circular disk-like elastic member 926 made of rubber. This sealing member 925 is configured so that the elastic member (an elastic part) 926 is fitted in a recessed portion 923h provided around a liquid inlet 923e of a battery case 923 to close the liquid inlet 923e from outside (from above in FIG. 24). While the elastic part 926 is compressed between the metallic lid member (a metallic lid part) 915 and the battery case 923, the circumferential edge portion 915m of the metallic lid part 915 is welded to the surrounding portion 923m of the battery case 923 so that the liquid inlet 923e is hermetically sealed by the elastic part 926. A sealed battery similar to this is disclosed in Patent Document 1 (see FIG. 5 and others of Patent Document 1).
This sealing member 925 is designed so that the size of the elastic part 926 in a radial direction (the size in a right-and-left direction in FIG. 24) is equal to the radial size of the recessed portion 923h so that the elastic part 926 is tightly fitted in the recessed portion 923h. Accordingly, even when the elastic part 926 is compressed between the metallic lid part 915 and the battery case 923, the elastic part 926 is not allowed to expand radially outward and thus the elastic part 926 is further applied with force from radially outside (from a side surface of the recessed portion 923h). In the elastic part 926, therefore, stress is generated in not only the thickness direction but also the radial direction. In this state, it is difficult for the elastic part 926 to keep hermeticity of the battery case 923 for a long period. In particular, since a sealed battery for use in a vehicle such as a hybrid car and an electric car is used for a long period, e.g., over 10 years, the hermeticity of the battery case 923 is demanded.
On the other hand, to solve the above problems, it is conceivable to set the radial size of the elastic part 926 to be smaller than the size of the recessed portion 923h to provide a clearance between the elastic part 926 and the recessed portion 923h in the radial direction. However, this configuration causes a new problem that it is difficult to accurately position the elastic part 926 in the recessed portion 923h. 
Furthermore, another sealing member 935 has been proposed in which, as shown in FIG. 25, an insertion portion 936 press-fitted in the liquid inlet 923e and an annular pressure-contact portion 937 formed integrally continuous to and around this insertion portion 936 are joined to the metallic lid part 915. This sealing member 935 utilizes the insertion portion 936 as a positioning guide and thus can accurately position the sealing member 935 with respect to the liquid inlet 923e. A sealed battery similar to this is disclosed in Patent Document 2 (see FIG. 2 and others of Patent Document 2).